Process for sterilizing a tight enclosure and installation for performing this process

Abstract

For sterilizing a tight enclosure (10) equipped with a ventilation and filtration circuit (14), said enclosure is isolated and the internal relative humidity level is lowered by means of an assembly (50) incorporating a drying cartridge (54). The sterilizing agent (46) is then introduced through a closed circuit (30) until a relative humidity level close to the dew point is obtained. The sterilizing agent is kept in the enclosure for a given contact time, before scavenging said agent by means of the ventilation and filtration circuit (14).

I claim: 
     
       1. Process for the sterilization of a tight enclosure having a closed volume and equipped with a ventilation and filtration circuit, which circuit has a supply pipe with a supply filter and a discharge pipe with a discharge filter, the supply pipe and the discharge pipe each connected to the tight enclosure defining the closed volume, the steps of the process comprising in order: (a) closing the ventilation and filtration circuit upstream of the supply filter and downstream of the discharge filter;   (b) while the ventilation and filtration circuit remains closed: I. drying the closed volume defined by the tight enclosure until a given lower relative humidity is obtained;   II. introducing a sterilizing agent into the closed volume until a given higher relative humidity is obtained, the sterilizing agent being introduced by using a closed circuit connected to the supply pipe upstream of the supply filter and to the discharge pipe downstream of the discharge filter;   III. sterilizing the closed volume by maintaining the sterilizing agent in the closed volume for given contact time; and     (c) scavenging the closed volume by opening and using the ventilation and filtration circuit, and wherein the drying of the closed volume is accomplished by circulating the atmosphere within said volume through a drying means which is located within the closed volume.   
     
     
       2. Process according to claim 1 wherein the lower relative humidity level is close to 30%. 
     
     
       3. Process according to claim 1 wherein the upper relative humidity level is close to 85%. 
     
     
       4. Process according to claim 1 wherein p-acetic acid is used as the sterilizing agent, the contact time being less than 1 hour. 
     
     
       5. Process of claim 1 wherein said given higher relative humidity corresponds to the saturation of the volume with sterilizing agent. 
     
     
       6. A system for performing a sterilization process comprising a tight enclosure defining a closed volume and equipped with a ventilation and filtration circuit, which circuit includes a supply pipe having a supply filter and a discharge pipe having a discharge filter, said system further comprising: a drying and stirring assembly within the enclosure, said assembly incorporating a fan, drying means, and filtration means connected in series; a sterilizing agent introduction circuit connected to the supply pipe upstream of the supply filter and connected to the discharge pipe downstream from the discharge filter, said circuit having in series a blower and an evaporator supplied with sterilizing agent via a sterilizing agent valve, said circuit further having inlet and outlet valves for isolating the circuit from the closed volume during sterilization; and   a relative humidity measuring probe within the closed volume and connected to a control means which automatically stops the introduction of sterilizing agent into the enclosed volume upon the relative humidity within the enclosed volume reaching a given upper relative humidity level.   
     
     
       7. The system of claim 6 wherein said control means automatically turns off said blower and automatically closes said sterilizing agent valve, inlet valve, and outlet valve upon the relative humidity within the enclosed volume reaching said given upper relative humidity level.